We shall study the structure and charge distribution of proteins in solution by investigating their dielectric properties. We have developed a new technique, dielectrophoresis, in which dipolar molecules migrate in an inhomogeneous A.C. electric field towards the region of maximum absolute field strength. At equilibrium, a concentration gradient is established which is proportional to the dipole moment; combined with conventional dielectric measurement, this allows the dipole moment and internal field to be separately determined. The rate of build-up and decay of the gradient are also measured, yielding a mobility and a diffusion constant. We will focus on modified proteins, either of allelic origin, or with deliberately substituted charge groups and pH vairation; their dipole moments should be highly sensitive to such changes. We will use H-1, C-13, F-19, O-17, and Cl-35 NMR relaxation to study the enzyme mechanism and mechanism of proton transfer of carbonic anhydrase and superoxide dismutase.